The present invention relates to a solar heat collector for heating buildings and other structures. More particularly, the present invention relates to an elongated solar heat collector through which a fluid medium is circulated and heated along two coaxially arranged flow paths.
U.S. Pat. No. 2,557,478 discloses a heating system that operates on solar energy. Solar heat collectors transfer solar energy to a liquid heat exchange medium such as water which is held in a large storage tank or reservoir in the structure to be heated. When the structure requires heat, a heat pump circulates a second heat exchange medium through an exchanger within the reservoir or circulates the heated medium itself through still other heat exchangers in a room or rooms of the structure calling for the heat. If a reversible heat pump is employed, it is possible to transfer heat away from the various rooms of the structure through the reservoir and heat collector. Thus, for example, in winter solar heat may be collected during daylight hours for heating a structure throughout the entire day. In summer, heat may be removed from the structure during the daylight hours for cooling and released through the solar collector at night.
Obviously, the efficiency of the solar heat collector is of principal concern in a heating system such as that shown and described in the identified patent. Regardless of the type of heat exchange medium employed, it is desirable that the medium be exposed to collected solar energy over the greatest possible portion of its flow path through the collector. In many prior art collectors, a fluid is circulated along coaxial fluid flow paths, however, direct conductive heating of the fluid through a tube wall occurs only along the outer path due the collector construction and the coaxial arrangement of the paths. U.S. Pat. No. 2,205,378 illustrates a solar energy collector of this type.
Elongated collectors with serially connected and coaxially arranged flow paths are desirable due to their compact construction. They can be mounted vertically either from the roof of a structure or a sidewall, and in such position they are selfcleaning in that dirt and other particles which reduce heat transfer coefficients either fall away from reflecting or heating surfaces or are washed away by weather elements. Improved efficiency of such collectors could be achieved by a design which allows the heat exchange medium circulated through the collector to be directly heated by solar energy along each of the coaxial flow paths.
Accordingly, it is a general object of the present invention to disclose a solar heat collector which permits a heat exchange medium circulated along coaxially arranged, serially connected flow paths to be heated by solar energy in substantially the same manner along both flow paths.